The invention relates to a method of controlling a transmission, and more particularly a method of controlling a transmission applicable to practice in a vehicle including a service module actuatable by a driver of the vehicle to request a desired gear, and in which the service module is connected to a control system for the transmission which automatically switches gears as a result of an actuation of the service module.
A method of this type is disclosed, for example, in WO 97/44210.
The method described therein is used for the control of a manually operated, non-synchronized vehicle transmission of conventional design having a plurality of gears which are operated, in part, automatically, by means of an electronic control system for the transmission, hereinafter also referred to as a xe2x80x9ctransmission control system,xe2x80x9d and an electrical/pneumatic actuating device connected to same. The automation relates to the carrying out of the mechanical movements which are necessary to switch gears by the electrical/pneumatic actuating device as a result of triggering signals generated by the transmission control system.
In a transmission control system of this type, an operating unit or service module is provided, which is actuated by the driver for gear selection. The operating unit is not connected mechanically to the transmission as in conventional transmissions, but rather, transmits corresponding signals to the transmission control system when actuated.
The transmission is connected to the drive engine of the vehicle via a clutch which can be actuated by the driver, in such manner that it can be disconnected from the transmission. In accordance with the known method, the transmission control system produces an automated shifting of gears from the currently selected gear to the gear desired by the driver in response to an actuation, by the driver, of the operating unit. The transmission control system then transmits pertinent request signals to an engine control system, in addition to the triggering signals sent to the electrical/pneumatic actuating device. By these, the engine capacity is adapted in such manner that the transmission is temporarily left with zero force, so that the clutch need not be opened for a gear switching operation.
Due to the fact that a number of mechanical adjusting and positioning processes must be carried out in a gear shifting operation, such process lasts for a certain, non-negligible time. The traveling speed may decrease or increase during such time span, depending on whether the vehicle is on an even road, climbing a hill, or going down a hill. The possibility exists, therefore, that the gear selected and desired by the driver can no longer be entered because the engine rpm""s at the vehicle speed at such later time would no longer be within an acceptable or desirable rpm range. In such case, the driver would have to initiate a gear shifting operation for a second time, resulting in further lengthening of the time required for the overall gear shifting process. Furthermore, as a result of such delay, the vehicle speed may also drop or increase in an undesirable manner.
Another method of controlling a transmission is disclosed, for example, in U.S. Pat. No. 4,852,906. The method described therein is limited to down-shifting, i.e., a shifting of gears for purposes of increasing the gear ratio of the transmission. Furthermore, in accordance with such disclosed method, it is not possible to change the gear ratio gear by gear. Instead, the gear with the highest gear ratio is always selected. This may result in violent, jolt-like reactions of the vehicle.
It is therefore an object of the present invention to provide a comfortable and universally applicable method of controlling a non-synchronized transmission which permits rapid shifting of gears.
In accordance with this and other objects of the invention, a method is provided for controlling a transmission of an engine-driven vehicle having several gears. The vehicle includes a service module actuatable by a driver of the vehicle to request a desired gear which is connected to a control system for the transmission. The control system for the transmission automatically switches gears as a result of an actuation of the service module. According to the method a transmission input speed and a transmission output speed is monitored, and based upon these speeds, continuous verification is made during a gear changing operation whether the engine speed will lie within an admissible rotational speed range of the engine as a result of engagement of the desired gear.
The invention provides the advantage that the time required for a shifting of gears is considerably shorter as compared with practice of previously known approaches. As a result, the driver will be given the impression that the transmission control system is carrying out the rapid gear shifting processes generally desired by drivers. It is a further advantage that the method in accordance with the invention can be carried out automatically in most of the numerous vehicle models and under the most diverse application conditions, such as, for example, mountain driving or different vehicle loads, without requiring additional measures or adjustments by the driver. As a result, the driver is relieved from having to evaluate the travel situation with respect to gear changes.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements and signals.